The marine environment has proven to be the richest reservoir of novel FPs on the planet. The upper photic ocean is stably monochromatic with downwelling daylight becoming primarily blue (470-490 nm) in color with increasing depth. Over millions of years this stable monochromatic spectral environment likely facilitated the evolution of fluorescent molecules that absorb and re-emit high-energy blue wavelengths into longer, lower energy colors. To date, the two major families of fluorescent molecules with sufficient molar brightness (high cross sections and quantum yield) and expression to produce a fluorescent signal that is visually evident to humans, GFP and the current bilirubin binding proteins discussed here, have evolved exclusively in marine organisms.
The first GFP was discovered in a hydrozoan jellyfish, Aequorea victoria, coupled to the bioluminescent apparatus, converting blue bioluminescent light to green. GFP orthologs were later found in non-bioluminescent anthozoas, primarily scleractinian corals. GFP orthologs have also been discovered in a few additional marine organisms including planktonic copepods, lancelets, and a ctenophore. However, it was recently discovered that fluorescence is not only phylogenetically widespread, but is also phenotypically variable across both cartilaginous and bony fishes.
The discussion above is merely provided for general background information and is not intended to be used as an aid in determining the scope of the claimed subject matter.